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Management Management Information Systems, Information Systems,

10/e10/eRaymond McLeod and George Raymond McLeod and George

Schell Schell

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Chapter 6Chapter 6

Database Management Database Management Systems Systems

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Learning ObjectivesLearning Objectives

► Understand the hierarchy of data.Understand the hierarchy of data.► Understand database structures and how they Understand database structures and how they

work.work.► Know how to relate tables together in a Know how to relate tables together in a

database.database.► Recognize the difference between a database Recognize the difference between a database

and a database management system.and a database management system.► Understand the database concept.Understand the database concept.► Know two basic methods for determining data Know two basic methods for determining data

needs.needs.

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Learning Objectives (Cont’d)Learning Objectives (Cont’d)

► Understand entity-relationship diagrams and Understand entity-relationship diagrams and class diagrams.class diagrams.

► Know the basics of reports and forms.Know the basics of reports and forms.► Understand the basic difference between Understand the basic difference between

structured query language and query-by-structured query language and query-by-example.example.

► Know about the important personnel who are Know about the important personnel who are associated with databases.associated with databases.

► Know the advantages and costs of database Know the advantages and costs of database management systems.management systems.

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Data HierarchyData Hierarchy

►Data fieldData field is the smallest unit of data. is the smallest unit of data.►RecordRecord is a collection of related data is a collection of related data

fields.fields.►FileFile is a collection of related records. is a collection of related records.►DatabaseDatabase is a collection of related is a collection of related

files.files. General definitionGeneral definition Restrictive definitionRestrictive definition

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DatabaseDatabase

► Table of rows & columns can be represented in Table of rows & columns can be represented in a spreadsheet.a spreadsheet.

►Relational database structureRelational database structure is is conceptually similar to a collection of related conceptually similar to a collection of related tables.tables.

► Flat fileFlat file is a table that does not have repeating is a table that does not have repeating columns; 1columns; 1stst normal form. normal form.

►NormalizationNormalization is a formal process for is a formal process for eliminating redundant data fields which eliminating redundant data fields which preserving the ability of the database to add, preserving the ability of the database to add, delete, and modify records without causing delete, and modify records without causing errors.errors.

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Figure 6.1 Spreadsheet as a Figure 6.1 Spreadsheet as a Simple DatabaseSimple Database

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Database (Cont’d)Database (Cont’d)

►KeyKey in a table is a field (or combination of in a table is a field (or combination of fields) that contain a value that uniquely fields) that contain a value that uniquely identifies each record in the table.identifies each record in the table.

► Candidate keyCandidate key is a field that uniquely is a field that uniquely identifies each table row but is not the identifies each table row but is not the chosen key.chosen key.

► Relating tables is done through sharing a Relating tables is done through sharing a common field & the value of the field common field & the value of the field determines which rows in the tables are determines which rows in the tables are logically joined.logically joined.

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Database Management Database Management SystemSystem

►Database management system Database management system (DBMS)(DBMS) is a software application that is a software application that stores the structure of the database, stores the structure of the database, the data itself, relationships among the data itself, relationships among data in the database, and forms & data in the database, and forms & reports pertaining to the database.reports pertaining to the database. Self-describing set of related data.Self-describing set of related data.

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Database StructuresDatabase Structures

►HierarchicalHierarchical is formed by data is formed by data groups, subgroups, and further groups, subgroups, and further subgroups; like branches on a tree.subgroups; like branches on a tree. Worked well with TPSs.Worked well with TPSs. Utilized computer resources efficiently.Utilized computer resources efficiently.

►NetworkNetwork allows retrieval of specific allows retrieval of specific records; allows a given record to point records; allows a given record to point to any other record in the database.to any other record in the database.

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Figure 6.2 Hierarchical Figure 6.2 Hierarchical StructureStructure

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Database Structures (Cont’d)Database Structures (Cont’d)

►RelationalRelational is when the relationship is when the relationship between tables are implicit.between tables are implicit.

►Physical relationshipPhysical relationship is when the is when the database structure (hierarchical, database structure (hierarchical, network) rely on storage addresses.network) rely on storage addresses.

►Implicit relationshipImplicit relationship is when the is when the database structure (relational) can be database structure (relational) can be implied from the data. implied from the data.

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A Relational Database A Relational Database ExampleExample

►A database named A database named ScheduleSchedule has been created has been created from tables used earlier in the chapter and some from tables used earlier in the chapter and some othersothers

►The database is implemented in Microsoft The database is implemented in Microsoft Access 2002 (also known as Access XP).Access 2002 (also known as Access XP).

►Databases break information into multiple tables Databases break information into multiple tables because if information were stored in a single because if information were stored in a single table, many data field values would be table, many data field values would be duplicated.duplicated.

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ScheduleSchedule Database Database

► The example is implemented on Microsoft Access DBMS but The example is implemented on Microsoft Access DBMS but would be similar on any relational DBMS product.would be similar on any relational DBMS product.

► The COURSE table in Access (Figure 6.4) is a list of data field The COURSE table in Access (Figure 6.4) is a list of data field values. The table itself had to be defined in Access before values values. The table itself had to be defined in Access before values were entered into the data fields. were entered into the data fields.

► Figure 6.5 shows the definition of the Figure 6.5 shows the definition of the CodeCode field. field.► Figure 6.6 illustrates that Figure 6.6 illustrates that AbbreviationAbbreviation field values will be field values will be

looked up from a list of values in the DEPARTMENT table.looked up from a list of values in the DEPARTMENT table.► Table 6.7 shows a single table of course and department fields Table 6.7 shows a single table of course and department fields

before they were separated into different tables.before they were separated into different tables.

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Figure 6.4 The COURSE TableFigure 6.4 The COURSE Table

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Figure 6.5 Defining the CODE Figure 6.5 Defining the CODE FieldField

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Figure 6.6 Look-up ValuesFigure 6.6 Look-up Values

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Table 6.7Table 6.7

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Figure 6.7 Access ViewFigure 6.7 Access View

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Database ConceptDatabase Concept

►Database conceptDatabase concept is the logical integration is the logical integration of records across multiple physical locations.of records across multiple physical locations.

►Data independenceData independence is the ability to make is the ability to make changes in the data structure without changes in the data structure without making changes to the application programs making changes to the application programs that access the data.that access the data.

►Data dictionaryData dictionary includes the definition of includes the definition of the data stored within the database & the data stored within the database & controlled by the database management controlled by the database management system.system.

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Creating a DatabaseCreating a Database

►Determine data that needs to be Determine data that needs to be collected & stored is a key step.collected & stored is a key step.

►Process-oriented approachProcess-oriented approach Define the problem.Define the problem. Identify necessary decisions.Identify necessary decisions. Describe information needs.Describe information needs. Determine the necessary processing.Determine the necessary processing. Specify data needs. Specify data needs.

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Determine Data Needs Determine Data Needs (Cont’d)(Cont’d)

►Enterprise modeling approachEnterprise modeling approach takes a broad view of the firm’s data takes a broad view of the firm’s data resources; all areas are considered, & resources; all areas are considered, & synergy of data resources between synergy of data resources between business areas can be leveraged.business areas can be leveraged. Result: Result: Enterprise data modelEnterprise data model

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Figure 6.8 Enterprise Data Figure 6.8 Enterprise Data ModelModel

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Data Modeling TechniquesData Modeling Techniques

►Entity-relationship diagrams (ERDs)Entity-relationship diagrams (ERDs) is a graphical representation of data in is a graphical representation of data in entities and the relationships between entities and the relationships between entities.entities.

►EntityEntity is a conceptual collection of is a conceptual collection of related data fields.related data fields.

►RelationshipRelationship is defined between entities. is defined between entities. One-to-one – 1:1One-to-one – 1:1 One-to-many – 1:MOne-to-many – 1:M Many-to-many – M:NMany-to-many – M:N

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Figure 6.11 Entity-relationship Figure 6.11 Entity-relationship DiagramDiagram

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Diagramming Techniques Diagramming Techniques (Cont’d)(Cont’d)

►Class DiagramClass Diagram is a graphical is a graphical representation of both the data used in representation of both the data used in an application and the actions an application and the actions associated with the data; object-oriented associated with the data; object-oriented design modeldesign model

►ObjectsObjects are the data, actions taken on are the data, actions taken on the data, & relationship between objects.the data, & relationship between objects.

►Class diagrams consist of the named Class diagrams consist of the named class, fields in the class, & actions class, fields in the class, & actions ((methodsmethods) that act upon the class.) that act upon the class.

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Figure 6.13 Class DiagramFigure 6.13 Class Diagram

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Using the DatabaseUsing the Database

►FormsForms show 1 record at a time & can show 1 record at a time & can be used to add, delete, or modify be used to add, delete, or modify database records.database records. NavigationNavigation AccuracyAccuracy ConsistencyConsistency FilteringFiltering subformssubforms

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Figure 6.15 Combined Data Figure 6.15 Combined Data Entry FormEntry Form

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Using the Database (Cont’d)Using the Database (Cont’d)

►ReportsReports are aggregated data from the are aggregated data from the database that are formatted in a database that are formatted in a manner that aids decision making.manner that aids decision making.

►QueriesQueries is a request for the database is a request for the database to display selected records.to display selected records.

►Query-by-example (QBE)Query-by-example (QBE) presents a presents a standardized form that the user standardized form that the user completes so the system can generate completes so the system can generate a true query.a true query.

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Figure 6.16 Report of Figure 6.16 Report of DepartmentsDepartments

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Structured Query LanguageStructured Query Language

►Structured query language (SQL)Structured query language (SQL) is the code that RDBMSs use to is the code that RDBMSs use to perform their database tasks.perform their database tasks.

►Method of choice for interacting with Method of choice for interacting with web-based databases.web-based databases.

►Writing SQL statements are not Writing SQL statements are not difficult for most manager’s data difficult for most manager’s data needs.needs.

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Figure 6.20 SQL CodeFigure 6.20 SQL Code

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Advanced Database Advanced Database ProcessingProcessing

►On-line analytical processing (OLAP)On-line analytical processing (OLAP) allows data analysis similar to statistical allows data analysis similar to statistical cross-tabulation.cross-tabulation.

►Data miningData mining, , data martsdata marts, & , & data data warehousingwarehousing focus on methodologies that focus on methodologies that offer users quick access to aggregated data offer users quick access to aggregated data specific to their decision-making needs.specific to their decision-making needs.

►Knowledge discoveryKnowledge discovery analyzes data analyzes data usage & data commonality among different usage & data commonality among different tables.tables.

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Database PersonnelDatabase Personnel

►Database Administrator (DBA)Database Administrator (DBA) is is an expert in developing, providing, an expert in developing, providing, and securing databases; duties includeand securing databases; duties include Database planning;Database planning; Database implementation;Database implementation; Database operation;Database operation; Database security.Database security.

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Database Personnel (Cont’d)Database Personnel (Cont’d)

►Database programmerDatabase programmer writes code writes code to strip and/or aggregate data from to strip and/or aggregate data from the databasethe database High level of specialization & selectionHigh level of specialization & selection

►End userEnd user generates reports & forms, generates reports & forms, post queries to the database, & use post queries to the database, & use results from their database inquiries to results from their database inquiries to make decisions that affect the firm & make decisions that affect the firm & its environmental constituents. its environmental constituents.

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DBMSs in PerspectiveDBMSs in Perspective

►DBMS AdvantagesDBMS Advantages Reduce data redundancy.Reduce data redundancy. Achieve data independence.Achieve data independence. Retrieve data & information rapidly.Retrieve data & information rapidly. Improve security.Improve security.

►DBMS DisadvantagesDBMS Disadvantages Obtain expensive software.Obtain expensive software. Obtain a large hardware configuration.Obtain a large hardware configuration. Hire and maintain a DBA staff.Hire and maintain a DBA staff.